import 'package:pull_to_refresh/pull_to_refresh.dart';

  List<String> items = ["1", "2", "3", "4", "5", "6", "7", "8"];
  RefreshController _refreshController =
      RefreshController(initialRefresh: false);

  void _onRefresh() async{
    // monitor network fetch
    await Future.delayed(Duration(milliseconds: 1000));
    // if failed,use refreshFailed()
    _refreshController.refreshCompleted();
  }

  void _onLoading() async{
    // monitor network fetch
    await Future.delayed(Duration(milliseconds: 1000));
    // if failed,use loadFailed(),if no data return,use LoadNodata()
    items.add((items.length+1).toString());
    if(mounted)
    setState(() {

    });
    _refreshController.loadComplete();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SmartRefresher(
        enablePullDown: true,
        enablePullUp: true,
        header: WaterDropHeader(),
        footer: CustomFooter(
          builder: (BuildContext context,LoadStatus mode){
            Widget body ;
            if(mode==LoadStatus.idle){
              body =  Text("pull up load");
            }
            else if(mode==LoadStatus.loading){
              body =  CupertinoActivityIndicator();
            }
            else if(mode == LoadStatus.failed){
              body = Text("Load Failed!Click retry!");
            }
            else if(mode == LoadStatus.canLoading){
                body = Text("release to load more");
            }
            else{
              body = Text("No more Data");
            }
            return Container(
              height: 55.0,
              child: Center(child:body),
            );
          },
        ),
        controller: _refreshController,
        onRefresh: _onRefresh,
        onLoading: _onLoading,
        child: ListView.builder(
          itemBuilder: (c, i) => Card(child: Center(child: Text(items[i]))),
          itemExtent: 100.0,
          itemCount: items.length,
        ),
      ),
    );
  }

  // from 1.5.0, it is not necessary to add this line
  //@override
 // void dispose() {
    // TODO: implement dispose
  //  _refreshController.dispose();
  //  super.dispose();
 // }

    // Smart Refresher under the global configuration subtree, here are a few particularly important attributes
     RefreshConfiguration(
         headerBuilder: () => WaterDropHeader(),        // Configure the default header indicator. If you have the same header indicator for each page, you need to set this
         footerBuilder:  () => ClassicFooter(),        // Configure default bottom indicator
         headerTriggerDistance: 80.0,        // header trigger refresh trigger distance
         springDescription:SpringDescription(stiffness: 170, damping: 16, mass: 1.9),         // custom spring back animate,the props meaning see the flutter api
         maxOverScrollExtent :100, //The maximum dragging range of the head. Set this property if a rush out of the view area occurs
         maxUnderScrollExtent:0, // Maximum dragging range at the bottom
         enableScrollWhenRefreshCompleted: true, //This property is incompatible with PageView and TabBarView. If you need TabBarView to slide left and right, you need to set it to true.
         enableLoadingWhenFailed : true, //In the case of load failure, users can still trigger more loads by gesture pull-up.
         hideFooterWhenNotFull: false, // Disable pull-up to load more functionality when Viewport is less than one screen
         enableBallisticLoad: true, // trigger load more by BallisticScrollActivity
        child: MaterialApp(
            ........
        )
    );

    MaterialApp(
            localizationsDelegates: [
              // this line is important
              RefreshLocalizations.delegate,
              GlobalWidgetsLocalizations.delegate,
              GlobalMaterialLocalizations.delegate
            ],
            supportedLocales: [
              const Locale('en'),
              const Locale('zh'),
            ],
            localeResolutionCallback:
                (Locale locale, Iterable<Locale> supportedLocales) {
              //print("change language");
              return locale;
            },
    )

   //error
   SmartRefresher(
      child: ScrollBar(
          child: ListView(
             ....
      )
    )
   )

   // right
   ScrollBar(
      child: SmartRefresher(
          child: ListView(
             ....
      )
    )
   )

   //error
   SmartRefresher(
      child:MainView()
   )

   class MainView extends StatelessWidget{
       Widget build(){
          return ListView(
             ....
          );
       }

   }